Evaporators that function to cool air that flows in contact with the evaporators have a variety of applications. In many instances, the air that is directed to the evaporators for cooling contains moisture that condenses to form frost and ice at the evaporators, thereby, among other undesirable consequences, compromising the efficient operation of the evaporators. For example, refrigeration appliances such as household refrigerators are routinely provided with evaporators that can serve to cool both the freezer compartments and the fresh food compartments of the refrigerators by cooling air delivered to the evaporators and supplying the cooled air to the freezer and fresh food compartments. Oftentimes, at least a portion of the air that is directed to the evaporators for cooling comprises air that is recirculated to the evaporators from the fresh food compartments of the refrigerators. Typically the recirculated air is at a temperature such that the air contains significant quantities of moisture that can be deposited at the evaporators as frost and ice. Heaters can be provided at the evaporators for intermittently defrosting the frost and ice that has accumulated at the evaporators. However, the heaters cannot in all circumstances maintain the evaporators frost- and ice-free to an extent required for the efficient operation of the evaporators because the amount of heat that can be applied by the heaters can be limited by other considerations.